ABSTRACT
Natural materials are gaining interest as coating feedstock because their "quality to cost" ratio is better and they are more environmentally friendly than most of the synthetic ceramics. They give sufficient protection to metal surfaces against harsh conditions such as corrosion, wear, and high temperature. In the current study, chromite mineral was beneficiated and reduced to two different sizes to be used as feedstock material for thermal spray coating. Powders were upgraded by gravity and magnetic separation, respectively, and thermally sprayed onto mild steel samples by using atmospheric plasma spray (APS) equipment. Morphology, structure, phases, elemental distribution of chromite powder, and coatings were studied using field emission scanning electron microscopy, X-ray diffraction, X-ray fluorescence spectroscopy, and energy-dispersive X-ray spectroscopy. Tribological properties of APS chromite coatings were investigated by using a ball-on-disk tribometer, and corrosion resistance properties were evaluated by carrying out potentiodynamic polarization testing in 3.5% NaCl solution. It is observed that the coating has better wear and corrosion resistance and is worn by abrasive wear that includes scratching and particles pull out. Coating efficiency, surface morphology, and microhardness of the coating developed by fine powder were better than those of coarse powder coating.
ABSTRACT
Biomedical implants are the need of this era due to the increase in number of accidents and follow-up surgeries. Different types of bone diseases such as osteoarthritis, osteomalacia, bone cancer, etc., are increasing globally. Mesoporous bioactive glass nanoparticles (MBGNs) are used in biomedical devices due to their osteointegration and bioactive properties. In this study, silver (Ag)- and strontium (Sr)-doped mesoporous bioactive glass nanoparticles (Ag-Sr MBGNs) were prepared by a modified Stöber process. In this method, Ag+ and Sr2+ were co-substituted in pure MBGNs to harvest the antibacterial properties of Ag ions, as well as pro-osteogenic potential of Sr2 ions. The effect of the two-ion concentration on morphology, surface charge, composition, antibacterial ability, and in-vitro bioactivity was studied. Scanning electron microscopy (SEM), X-Ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) confirmed the doping of Sr and Ag in MBGNs. SEM and EDX analysis confirmed the spherical morphology and typical composition of MBGNs, respectively. The Ag-Sr MBGNs showed a strong antibacterial effect against Staphylococcus carnosus and Escherichia coli bacteria determined via turbidity and disc diffusion method. Moreover, the synthesized Ag-Sr MBGNs develop apatite-like crystals upon immersion in simulated body fluid (SBF), which suggested that the addition of Sr improved in vitro bioactivity. The Ag-Sr MBGNs synthesized in this study can be used for the preparation of scaffolds or as a filler material in the composite coatings for bone tissue engineering.
